The present invention relates to the field of shoring systems for supporting the sides of a trench or hole in the ground and, in particular, sheeting panels for hydraulic shoring techniques.
Various shoring techniques have been employed for supporting the sides of a trench or hole in the ground during excavation. One shoring technique, called “aluminum hydraulic shoring,” employs hydraulic jacks, aluminum shoring rails, and shoring sheeting panels to support the sides of the trench. After a portion of the trench is excavated, two sheeting panels may be placed substantially parallel to one another on opposite sides of the trench. The shoring rails, typically already connected by the hydraulic jacks, are then placed on the faces of the two sheeting panels. The hydraulic jacks extend perpendicularly from the face of one sheeting panel to the face of the second sheeting panel. After proper placement of the shoring rails and hydraulic jacks, the hydraulic cylinders within the jacks are pressurized. Alternatively, the hydraulic shoring rails may be fastened to the sheeting panels, and then the assembly of rails and panels may be placed in the trench.
In 1989, the Occupational Safety and Health Administration (OSHA) adopted Federal Standard 29 CFR 1926, Subpart-P establishing safety requirements for excavation work-sites. In particular, Regulation 1926, Subpart-P, Appendix D includes item (g)(7) identifying the types of shore sheeting that may be used for aluminum hydraulic shoring for trenches. Item (g)(7) states: “Plywood shall be 1.125 inch thick softwood or 0.75 inch thick, 14 ply, arctic white birch (Finland form). Please note that plywood is not intended as a structural member, but only for prevention of local raveling (sloughing of the trench face) between shores.”
The OSHA Subpart P Standard also requires (i) manufacturers of shoring equipment to develop their own tabulated data for the aluminum hydraulic shoring equipment they develop, and (ii) users of the equipment to adhere to the data developed for the shoring rails and sheeting panels they are using. To afford themselves broader liability protection, most manufacturers of hydraulic shoring have tried to stay as close as possible to the data developed by OSHA. Other types of sheeting such as steel plate and plywood with performance equivalent to and even less than three-quarter-inch, 14 ply, Artic White Birch (Finland form or “Finnform”) have been allowed. Finnform plywood is a relatively difficult standard to meet or exceed so it is used as the calibration standard within the industry.
To date, plywood has primarily been used for shoring sheeting panels. Although plywood performs well as a shoring panel, the material also has a number of drawbacks. In particular, water, mud, and drying cause the plywood panels to gray and eventually delaminate. The handling and installation of plywood panels also breaks the corners of the plywood panels. Thus, the useful life of plywood sheeting panels is approximately one to two years.
Additionally, plywood breaks and punctures relatively easily. If a plywood sheeting panel is punctured or an edge of the panel is broken, the overall area of restraint provided by the panel is reduced. Unrestrained areas of soil and rock may shift and move, creating potential safety hazards.
As noted, plywood sheeting panels can be damaged during handling, which may include dragging the panel. Over time, the panel becomes bent in the face plane, and breaking and splintering occurs on the face of the panel. As the deterioration progresses, the coverage and effectiveness of the sheeting becomes less than intended. Furthermore, splintering on the edges and face of the plywood present a safety hazard to workers handling the shores (e.g., the assembly of shore rails and sheeting panels). Even with gloves on, large plywood splinters can penetrate the hands and other parts of the body. Workers inside the trench that are not handling the shores can still brush up against the shore, receiving puncture wounds. Working at the trench level exposes the upper body and head to the surrounding shoring sheeting.
To combat these issues, metal edge protectors may be installed on plywood sheeting panels, and the shores may be cleaned and refurbished after each use. The cost and time associated with replacing the plywood panels, installing metal edge protectors, and cleaning the shores can be excessive.
Therefore, a need exists for an improved sheeting panel that meets or exceeds the OSHA regulations for aluminum hydraulic shoring for trenches. More particularly, there exists a need for a sheeting panel that reduces the long-term cost of maintaining and installing shoring systems and is durable, easy to handle and maintain, and safe for both shore installers and workers inside the trench.